This invention relates generally to a bicomponent or multi-component extruded monofilament used as a vegetation cutting line for a rotating trimmer. More particularly, the invention relates to an extruded monofilament cutting line having wear resistant edges, and, in a particular embodiment, replenishing wear-resistant edges imbedded within an abrasion or non-abrasion resistant sheath. The present invention also relates to an extruded monofilament cutting line containing an embedded grit or abrasive material. The present invention further relates to an extruded monofilament cutting line containing a high density material to increase the force of the impact between the cutting line and the vegetation.
Vegetation cutting devices are well known in the art. These devices, including rotating trimmers, typically employ monofilament cutting or trimming line for cutting overgrown vegetation such as grass and weeds, edging lawns around borders and concrete, and trimming grass in places that are hard to reach with lawn mowers. Smaller lines are typically used for trimming grasses, while fine blades and larger lines are typically used for cutting larger stalks of weeds or grasses and heavy growth.
Shaped monofilament cutting lines were introduced in the late 1980""s and have been shown to have significantly improved the cutting quality of weeds and like vegetation. By the term xe2x80x9cshapedxe2x80x9d, it is meant that the cutting line has a cross-sectional configuration other than round, which is the cross-sectional configuration of conventional monofilament cutting lines. More particularly, cross-sectional shapes other than round have been used because the edges or corners created by those shapes provide for cleaner cuts of the grass or weeds, resulting in less tearing of the blades of grass. In turn, less tearing of the blades of grass desirably results in less browning of the grass ends after cutting.
There are, however, at least two drawbacks to using these shaped monofilament lines. First, some of the shapes tend to damage the head of the rotating trimmer when it comes out of the head, since the outermost surface of the line is not smooth. Vice versa, the head may damage the trimmer line. Second, the shapes have been known to become worn during use, thereby reducing their improved effectiveness in the cut quality of the vegetation. That is, some of the edges and corners created by the cross-sectional shapes of the cutting line wear off, leaving a somewhat rounded strand that is less effective in cutting vegetation.
Various attempts have been made heretofore to overcome this problem. For example, U.S. Pat. No. 5,430,943 provides a shape-within-a-shape monofilament line. The patent proposes the use of a cutting element having a shaped inner cutting edge that is exposed for use after the outermost cutting edge has been worn away. However, this concept has proved to be limited by the number of shapes that can be designed, and it only uses a single component material in the construction of the monofilament cutting line.
Others have attempted to provide mono-component cutting lines with improved wear resistant properties. Ideally, blended resins and additives extruded to produce the cutting lines are selected to maximize the wear resistance and the impact properties of the monofilament cutting line. Unfortunately, it has been found that materials that provide the best results with respect to wear resistance do not generally provide the best results with respect to impact properties. Thus, a compromise is generally made to balance the performance of the monofilament cutting line. Additionally, it has been found that resins that provide the best wear resistance also have properties which cause defects such as voids, excessive out-of-roundness, or splitting, of the monofilament during extrusion.
Thus, the need exists for a monofilament cutting line exhibiting improved wear resistance as compared to other monofilament cutting lines while maintaining good impact properties, and, if desired, that is capable of protecting the head of the rotating trimmer.
It is therefore, an object of the present invention to provide a multi-component, extruded monofilament cutting line.
It is another object of the present invention to provide a multi-component monofilament cutting line having improved wear resistance and good impact properties.
It is still another object of the present invention to provide a multi-component monofilament cutting line that will neither damage nor be damaged by the head of the rotating trimmer in which it may be employed.
It is yet another object of the present invention to provide a multi-component monofilament cutting line having a smooth fiber surface when coming out of the trimmer head.
It is still another object of the present invention to provide a shaped multi-component monofilament cutting line that will maintain its cross-sectional configuration for a longer period of use.
It is yet another object of the present invention to provide a multi-component monofilament cutting line which can offer improved wear resistance without excessive voids, splitting or out-of-roundness.
It is a further object of the present invention to provide a multi-component monofilament cutting line with replenishing edges.
It is still a further object of the present invention to provide a multi-component monofilament cutting line having inner edges and outer edges, wherein the inner edges may be exposed after the outer edges have been worn down.
It is yet a further object of the present invention is to provide a multi-component monofilament cutting line containing an embedded grit or abrasive material.
It is yet an additional object of the present invention to provide a multi-component monofilament cutting line containing a high density material to increase, during use, the force of impact between the cutting line and vegetation.
At least one or more of the foregoing objects, together with the advantages thereof over the known art relating to monofilament cutting lines, which shall become apparent from the specification that follows, are accomplished by the invention as hereinafter described and claimed.
In general, aspects of the present invention are accomplished by providing an extruded monofilament cutting line for a rotary trimmer for cutting vegetation including a first component material; and a second component material, the same or different in chemical structure from the first component material and extruded separately from the first component material. The second component material provides the cutting line with cutting edges and has increased wear resistance properties and increased abrasion resistance properties compared to those same properties of the first component material.
Other aspects of the invention are provided by a monofilament cutting line for a rotary trimmer for cutting vegetation comprising a first component material having a specific gravity of about 1.15 g/cc or less; and a second component material having a specific gravity greater than 1.15 g/cc.
Still other aspects of the present invention are accomplished by providing a multi-component, monofilament cutting line for a rotary trimmer for cutting vegetation including at least a first component material; and at least a second component material, the same or different in chemical structure from the first component material but not blended with the first component material and extruded separately from the first component material. The second component material provides the cutting line with cutting edges. Notably, the multi-component, monofilament cutting line has increased wear resistance and increased abrasion resistance as compared to a single component monofilament cutting line employing one of either the first or second component materials.
Still other aspects of the present invention are accomplished by providing a monofilament cutting line including a first component material having an abrasive filler and/or a second component material providing a sheath surrounding the first component material.